Due to its portability, abundance and low cost, paper has drawn increasing interest as a platform for sensing devices, particularly in the field of point-of-care (POC) diagnostics and disease screening applications for the developing world.1 Currently, the main techniques to fabricate paper-based biosensors involve either conjugating the biological sensing elements to the paper surface by chemical modification of the paper fibers,2 entrapping these biomolecules within sol-gel derived inks,3 or localizing adsorbed biomolecules using hydrophobic barriers to define channels created by photolithography, etching, plasma treatment, flexographic or screen printing methods.4 However, such approaches can be laborious, prone to non-specific binding, and may require many complex reactions, which can make fabrication inconvenient and increase cost.
DNA aptamers have become important sensing elements due to their thermal and chemical stability, versatility in target recognition (from small molecules to whole cells), high affinity and specificity, and ease of synthesis and manipulation5—all inherent advantages over conventional antibody and enzyme-based sensors.6 However, aptamers have rarely been explored for paper-based diagnostics since they suffer from some of the same issues as proteins in their need for complex immobilization strategies or conjugation to species such as nanoparticles or microbeads for localization on paper.7 
Extremely long, tandem repeating DNA molecules can easily be produced by a biochemical technique known as rolling circle amplification (RCA)—an isothermal process in which a special DNA polymerase, such as φ29 DNA polymerase, extends a short DNA primer by making round-by-round copies of a circular DNA template8—and have been extensively explored for bioanalytical applications to detect a variety of targets,9 and for various nanotechnology applications.10 